We present spatially resolved high-spectral resolution observations of the 2.3
micron CO first overtone lines in the red supergiant Betelgeuse using AMBER at
the Very Large Telescope Interferometer (VLTI). For the first time, we have
succeeded in reconstructing spatially resolved spectra of the individual CO lines
for the inhomogeneous, dynamical atmosphere with a spectral resolution of 6000
and a spatial resolution of 9.8 mas — the highest spatial resolution achieved
for Betelgeuse. The observed spatially resolved spectrum reveals a pronounced,
asymmetrically extended atmosphere up to at least 1.3 stellar radii. Moreover,
the extended atmosphere appears differently across the CO line profiles because
of the vigorous motions of a large CO gas clump with velocities of 20—30 km/s.
Comparison between the CO line data taken in 2008 and 2009 shows a significant
change in the dynamics of the atmosphere. In contrast to the CO line data, the
continuum data taken in 2008 and 2009 reveal no or only marginal time variations,
much smaller than the maximum variation predicted by the current 3-D convection
simulations. Our AMBER observations suggest the following new picture: the
material within 1.5 stellar radii is strongly stirred possibly by
magnetohydrodynamical processes or pulsation and may be violently flung out
rather than spilling out in an ordered, spherical fashion as often assumed.

Exozodiacal dust: origin and impact on the study of extrasolar terrestrial planets

Denis Defrère (Université de Liège)

Most debris disks resolved so far show extended structures located at tens to hundreds AU from the host star, and are more analogous to our solar system’s dusty Kuiper belt than to the AU-scale zodiacal disk inside our solar system’s asteroid belt. Over the last few years however, a few hot debris disks have been resolved around a handful of main sequence stars thanks to the advance of infrared interferometry. The grain populations derived from these observations are quite intriguing, as they point toward very high dust replenishment rates, high cometary activity or major collisional events. In this talk, we review the ongoing effort to detect bright exozodiacal disks with precision near-infrared interferometry at the CHARA array with the FLUOR instrument. We discuss preliminary statistical trends on the occurrence of bright exozodiacal disks around nearby main sequence stars and show how this information can be used to constrain the global architecture and evolution of debris disks. Finally, we briefly address near-term prospects by discussing the ongoing instrumental developments of the FLUOR instrument.

Planets Twice the Size of Earth: Orbits, Radii, and Occurrence

Geoff Marcy (University of California, Berkeley)

The talk will report the observed distribution of planet radii, orbital distances, and occurrence frequency for planets with orbital periods less than 50 days around Solar-type stars. We draw from extensive Kepler measurements that offer good completeness for planets with radii as small as 2.0 Earth-radii.

Planets Twice the Size of Earth: Orbits, Radii, and Occurrence

Geoff Marcy (University of California, Berkeley)

The talk will report the observed distribution of planet radii, orbital distances, and occurrence frequency for planets with orbital periods less than 50 days around Solar-type stars. We draw from extensive Kepler measurements that offer good completeness for planets with radii as small as 2.0 Earth-radii.

More than 600 extrasolar planets have been detected so far and an intense characterisation effort has been undertaken to unveil the atmospheric properties of some of these distant worlds seen in transit accross their stars. A large number of transiting exoplanets are found in extreme irradiation environments, very close to their stars, and the question arise of whether the atmospheres of these planets remain stable or get blown away. Atmospheric evaporation was observed in some hot giant exoplanets or "hot jupiters", but does not significantly alter the fate of these massive objects ( 300 Earth masses). Hot neptunes, on the other hand, are a class of exoplanets with typical masses around 20x Earth. They are the link between hot jupiters and super-earths (1 to10 Earth masses). It is surmised that the latters can be evaporation remnants, with atmospheres completely eroded by the extreme stellar irradiation. In this case, could hot neptunes be the progenitors of the hot rocky planets detected by the Corot and Kepler missions ? Detecting their extended atmospheres and measuring their mass loss rates and atmospheric heating efficiencies are key steps towards the understanding of the atmospheric dynamics and properties of low-mass exoplanets. After an introduction about planetary transits, I will review the results we have obtained with HST on the atmospheric evaporation of transiting exoplanets, on both observational and theoretical sides. I will finally discuss the prospects about atmospheric characterisation for Earth-size planets in more temperate - habitable - environments, and how the upcoming transit of Venus in June 2012 and the PLATO mission proposed to ESA could lead to a new era where atmospheric characterisation is common for hundreds of Earth-like exoplanets.

Stirring Saturn’s magnetosphere with vortical winds in the upper atmosphere

Margaret Kivelson (UCLA)

Electromagnetic phenomena in Saturn’s magnetosphere and ionosphere vary periodically at a period close to that of planetary rotation. Arguments relating to the slow drift of the modulation period and the inertia of different regions of Saturn’s environment require that the system be driven from regions remote from the equatorial surface, plausibly the high altitude atmosphere. The assumption that the system is driven from the ionospheric ends of the flux tubes is supported by characteristics of the magnetic perturbations observed near the magnetic equator. This presentation will describe results from a magnetohydrodynamic simulation in which the atmosphere drives vortical winds in the southern ionosphere. The wind pattern rotates about the spin axis at the modulation period of Saturn Kilometric Radiation (SKR). The simulation reproduces many features reported for magnetospheric perturbations. It also exhibits field-aligned current (FAC) patterns that correspond to properties reported for SKR emissions. In a second run of the simulation, an additional vortical flow structure is introduced into the northern high-altitude atmosphere. The northern structure rotates about the spin axis at a slightly shorter period. This second simulation provides insight into the way in which two separate frequencies affect the magnetosphere and the FACs.